The present invention relates to construction materials for waterproofing, sealing and/or otherwise covering construction surfaces and to a method of manufacturing such materials. More particularly, the present invention relates to self-adhesive roofing materials that “partially adhere” to the underlying substrate surface. The present invention also relates to other self-adhesive materials for covering construction surfaces, such as a foundations, walls, roads or bridges, where “partial adhesion” to the underlying surface is advantageous. Such materials include, for example, insulation, foundation sealing material, road construction material and waterproofing materials for bridges and tunnels. The self-adhesive construction materials of the present invention permit easy and hassle-free field application, and good adhesion, while at the same time providing a ventilating mechanism that allows for lateral release (or venting) of potentially harmful pressure and latent moisture once the material is in place.
Waterproofing membranes are well known and commonly used in the roofing industry. It is also well known to use bituminous compositions to manufacture waterproofing materials that are generally used for roof covering and roofing underlayments. Modified bituminous roofing was invented in Europe in the 1960s, and has been used successfully in the United States for over 25 years. These materials are known in the industry as modified bituminous prepared roofing, and include modified bitumen roofing membranes. They typically comprise a carrier (or core) which is saturated and/or coated on one or both sides with a modified bituminous material. The carrier is typically a reinforcement support sheet made of fabric, such as polyester, fiberglass, or a combination of both. For some applications a simple film-based carrier such as a polyolefin (e.g. polybutadiene, polypropylene, or polyethylene) or polyester film may be used. The modified bituminous material comprises bitumen modified with a material that enhances its physical properties.
As used herein, the terms “modified bitumen” and “modified bituminous coating/layer” are defined as a composition comprising bitumen and any material that enhances the inherent physical properties of the bitumen and the resultant roofing membrane, such as heat stability, low temperature hardening point, and mechanical strength. The property enhancing material is referred to herein as the modifier. Bitumen modifiers are well known in the art and typically include synthetic polymers such as atactic polypropylene (APP), amorphous poly alpha olefin (APAO), polypropylene ethylene copolymers, polyethylene (PE), polyoxyethylene, thermoplastic polyolefin (TPO), styrene-butadiene-styrene (SBS), styrene-ethylene-butadiene-styrene (SEBS), sytrene-isoprene-styene (SIS), synthetic rubber, but may include any other materials having the desired physical property enhancing effect. The terms “unmodified bitumen” or “unmodified bituminous coating layer” are defined as a bituminous composition or layer comprising bitumen but no modifier, i.e. no material that enhances the bitumen's inherent physical properties.
As discussed above, use of modified bitumen imparts several desirable properties to the resultant roofing membrane. For example, when the carrier is saturated in and coated with a modified bitumen compound such that the modified bituminous compound penetrates the fibers and pores of the carrier, the resulting waterproofing material has good heat stability and low temperature flexibility, and consequently a wider service temperature range. Generally “low temperature” means around the freezing point, i.e. about 0 degrees Celsius, but could vary depending upon the intended application. Such membranes also possess good weatherability characteristics, as well as high strength and elongation properties, which provide resistance to roof movements, thermal induced fatigue and mechanical induced fatigue (e.g. to prevent cracks, to prevent damage from temperature fluctuations and to prevent physical damage, respectively). Different types of modifiers impart different characteristics to the membrane. For example, the typical softening point temperature of an APP modified bitumen compound is in excess of 150 degrees Celsius, whereas that of a conventional SBS modified bitumen compound is approximately 120 degrees Celsius. In addition, an APP modified compound utilized on the top surface offers plastomeric characteristics to the bitumen, making the membrane very hard and imparting improved flow resistance at high temperatures. U.S. Pat. Nos. 5,766,729, 5,843,522 and 5,964,946, to Zanchetta et al. relate to modified bituminous roofing membranes and are hereby incorporated by reference in their entirety.
Prior to the introduction of modified bitumen roofing membranes, built-up-roofing (BUR) was being used in the United States since the turn of the 20th century. BUR is manufactured by saturating and coating both sides of a reinforcement carrier support sheet made of organic felt or fiberglass with unmodified bituminous coating material. This method, however, generally requires in situ application of additional bitumen layers, which involves pouring hot bitumen onto the substrate surface, applying the BUR sheet on the hot bitumen, and pouring another layer of hot bitumen on top of the BUR sheet. While the unmodified bitumen used to coat the reinforcement during the manufacturing process may include a filler, the hot bitumen used during installation includes no additives at all.
The roofing membrane market is largely divided into two major classifications: commercial/industrial and residential applications. In both these markets there are two major types of modified bitumen roofing products. They are known as the “cap sheet” and “base sheet”.
The “cap sheet” takes its name from the fact that its top surface is exposed to the elements. The bituminous component of a cap sheet may be modified with a variety of modifiers, including atactic polypropylene (APP), amorphous poly alpha olefin (APAO), polypropylene ethylene copolymers, polyethylene (PE), polyoxyethylene, thermoplastic polyolefin (TPO), styrene-butadiene-styrene (SBS), styrene-ethylene-butadiene-styrene (SEBS), sytrene-isoprene-styene (SIS), synthetic rubber or other bituminous modifiers. The carrier component may be a polyester carrier, fiberglass or polyester/fiberglass combination mat or carrier. Cap sheets can be smooth or granule-surfaced. Modified bitumen membranes which do not have factory-applied granule or foil surfacing need some form of field-applied ultraviolet protective coating. The thickness of cap membranes is typically between 2.8 mm and 5.0 mm for both granulated and smooth (non-granulated) surfaces.
In most roofing systems a base sheet is applied under the cap sheet. The bituminous component of the base sheet can be modified using any of the same modifiers as the cap sheet. Because the base sheet is not intended to be exposed to the elements, the bituminous component is typically modified using smaller quantities of less expensive polymers such as atactic polypropylene (APP) or styrene-butadiene-styrene (SBS). A base sheet is generally reinforced with a fiberglass carrier (which is significantly less expensive than polyester) and is smooth surfaced. Its thickness typically ranges from 1.0 mm to 2.5 mm depending upon the job specifications.
Typically, cap and base sheet roofing systems are installed by first applying the base sheet to the substrate structure using either mechanical fasteners, hot mopping or cold adhesives, and then applying the cap sheets on top of the base sheets, with the seams of adjacent rolls in offset relation. The typical weight of a one square roll (1 roofing square equals 107.6 square feet) is between 70 pounds and 115 pounds, depending upon thickness of the membrane. Another type of waterproofing material used in roofing is the “underlayment”. Underlayments are commonly utilized under shingle roofing material, metal roofing panels or tile roofing to provide waterproofing characteristics. They are widely used in residential applications, and may also be specifically designed for use in regions with colder climates, where ice-dam protection may be highly desirable. An ice-dam occurs when water flows down the roof, gets trapped on protruding edges and freezes, thus causing a build up of ice, which may cause cracking. Ice-dam protection is an issue in steep-slope applications, which tend to be mostly residential. Typically, underlayments are reinforced with fiberglass, but can also have no carrier. In the latter case, they simply comprise a coating of self-adhesive waterproofing compound on a polyolefinic film. Because they are typically used in steep slope roofing applications, underlayments must provide good traction for the safety of the roofer installing the material. Underlayments are typically installed by mechanically fastening the underlayment to the plywood substrate, or adhering the underlayment to the plywood substrate using a cold adhesive compound.
The most popular methods of installing waterproofing materials, and in particular roofing membrane are: (1) torching; (2) hot mopping; (3) cold adhesives; (4) mechanical fastening; and (5) self-adhesion. Typically, BUR sheets are applied using hot mopping. They can also be applied using cold-adhesives instead of hot asphalt. In this case the BUR sheet is set onto the substrate surface using cold adhesives and then, depending upon construction specifications, one or more additional BUR sheets may be applied onto the BUR sheet either by hot mopping or again using cold adhesives. Most APP-modified bitumen membranes are torch-applied. Most SBS-modified bitumen membranes are installed using hot mopping, torching or cold adhesives. As discussed above, underlayments are typically installed using mechanical fastening or cold adhesives.
Torch application entails heating the backside of the sheet with an open flame to melt the bituminous compound and using the molten bitumen to form a heat weld between the membrane and the substrate. Hot mopping entails mechanically spreading a layer of hot asphalt on the underlying substrate structure and then applying the membrane over the hot asphalt layer. The cold adhesives method involves using cold adhesives such as those described in U.S. Pat. No. 5,807,911 issued to Drieskens, et al. instead of hot asphalt to adhere the membrane to the substrate. Mechanical fastening entails fastening the material to the substrate with mechanical means such as using nails or staples.
Finally self-adhesion involves the use of a self-adhesive layer protected by a release liner in the roofing material. The adhesive material in a self-adhesive membrane serves to affix the membrane to the substrate surface, e.g. the roof deck, base sheet or underlayment, and typically includes modifiers and tackifying resins. The self-adhesive layer is usually protected by a release liner that is typically made of film (such as polypropylene, polyethylene or polyester) or kraft paper, and is treated with a release agent, for example, a silicone adhesive. The release liner is typically treated with the release agent on both the side that comes in contact with the self-adhesive compound and the exposed side. The release liner is applied to the self-adhesive compound to prevent sticking between adjacent sections of the roofing material and between the roofing and the packaging when the finished membrane is formed into rolls and stored or transported. Examples of such release films are disclosed in U.S. Pat. Nos. 5,143,766, 5,082,704, 5,932,352, and 5,756,214. U.S. Pat. No. 5,143,766, to Wenz et al., describes a self-adhesive bituminous roofing and sealing web with a cover sheet. U.S. Pat. Nos. 5,082,704 and 5,932,352, to Higgins, describe a release film. U.S. Pat. No. 5,756,214 to Waldron et al. describes a release film comprising polycarbonate-silicone-urethane resin. U.S. Pat. No. 5,756,214 to Katsura et al. describes a polymeric release film. The aforementioned patents are hereby incorporated by reference in their entirety. The self-adhesive compound used in the self-adhesive material is typically factory applied to the membrane and provides an adhesive layer having sufficient surface tack (“quick grab”), as well as adequate strength for adhering the membrane to the substrate surface.
A typical self-adhesive membrane includes a reinforcement or carrier saturated with modified bituminous compound that supports a modified bituminous compound layer positioned on top of the carrier sheet, and a self-adhesive modified bituminous compound layer positioned below the carrier sheet. A high strength polyolefinic film is then applied on to the exposed surface of the adhesive compound. However, self-adhering membranes, e.g. some underlayments, can also not include reinforcement. These types of materials comprise a release liner such as siliconized kraft paper onto which a bituminous adhesive compound is applied. Examples of self-adhesive roofing materials are disclosed in U.S. Pat. Nos. 4,386,981, 4,670,071, 4,757,652, 6,360,506, and 6,641,896. U.S. Pat. No. 4,386,981, to Clapperton, describes a self-adhesive underlayment used in an inverted fashion. In this case, to facilitate ventilation of any entrapped moisture, the non-adhesive surface of the material is placed adjacent to the roof surface, leaving the adhesive surface exposed so as to provide an adhesive surface for application of a weathering layer such as a gravel coating on top. U.S. Pat. No. 4,670,071, to Cooper et al., describes a self-adhesive membrane having discontinuous apertures so that bitumen adheres to the deck over an area of 10-50% of the total sheet, thus allowing water vapor passing through the sheet to escape laterally. U.S. Pat. No. 4,757,652, to Kalkanoglu, describes a self-adhering roofing product with a two-section release liner. U.S. Pat. No. 6,360,506, to Graae, teaches a bituminous roofing membrane and method of joining two roofing membranes with self-sticking strips. U.S. Pat. No. 6,641,896, to Fensel, describes a water resistant fire retardant underlayment sheet material having a self-adhesive bitumen layer. These patents also are incorporated by reference herein in their entirety.
Each of the available methods of application has some disadvantage. In the “torch” application technique, propane gas burners or torches are used to heat the back surface of the rolls. The flame has a temperature of 1,000 to 1,300 degrees Celsius and is directed towards the bottom surface of the sheet. Torching can thus be a dangerous undertaking due to the risk of fire caused by the utilization of a torch and similar equipment.
Hot mopping eliminates the use of the torch, but instead requires drums or cartons of hot asphalt. While it reduces the risk of fire, it creates additional operational problems. For example, hot mopping is labor intensive, especially in larger projects, and results in waste cartons with chemical residue, that must be disposed of properly. The disposal itself is also costly and labor-intensive. While this problem can be eliminated by using a hose to pump the asphalt to the roof, it is very difficult and dangerous to do so, especially in high-rise buildings installations.
Because cold adhesives generally come in buckets or pressurized spray can systems, their use also poses problems related to disposal of empty buckets or aerosol cans. Additionally, cold adhesives contain solvents that are not desirable from an environmental point of view and have a potential for the release of airborne pollutants.
Mechanical fastening is a slow and cumbersome process, which labor intensive and not always appropriate.
Self-adhesion has many advantages over the other methods. It permits a more simplified, safer and economical roof installation without compromising structural integrity and lap sealing capabilities. It also reduces labor and installation costs, and volatile organic compound and other emissions associated with the other methods of installation. Easy installation results from the fact that the self-adhesive compound is typically factory applied under controlled conditions prior to use in the field. The fact that the tacky self-adhesive is applied under controlled conditions, rather than in the field where there is a risk of contamination and variability in application techniques, allows for a consistently properly placed adhesive and enhanced adhesion to the underlying substrate. As a result, commercially available self-adhesive roofing materials are used in both commercial and residential applications.
While solving many of the problems of the installation techniques, self-adhesive materials do have drawbacks. These drawbacks are mainly due to their enhanced capacity for complete adhesion. For example, in comparison to mechanical attachment, attaching a self-adhesive base sheet to the underlying substrate (e.g. plywood, concrete or insulation) results in a fully adhered roofing system. This can be problematic because such full adhesion does not allow for ventilation of the roof or surface when necessary. Ventilation is important because it allows escape of moisture or condensation that can accumulate between the substrate surface and the roofing material due to, for example, thermal fluctuations (i.e. differences in temperatures between the outside and inside of a structure). A deck made of plywood that is fully adhered to the roofing membrane can be damaged over a period of time if this moisture is not allowed to escape. Furthermore, total adhesion of the roofing membrane to a plywood deck can be problematic when re-roofing is necessary, because there is a higher risk of damaging the underlying surface during roof tear-off. Proper ventilation is also necessary when the roofing membrane is applied to substrates other than plywood, such as concrete. Lightweight concretes, which are commonly used as part of the roof insulation, are prepared using ingredients such as Portland cement and water, and are poured onto the rooftop. Later roofing membranes are installed over the concrete surface that is formed. If a membrane that does not allow for proper ventilation is installed before the concrete is sufficiently cured, moisture and other gases may become entrapped in the concrete. This may result in blister formation on the membrane, and could eventually lead to rotting and decaying of both the concrete substrate and membrane. Similarly, full adhesion is undesirable when installing roofing membranes over insulations such as polyisocyanurate (Polylso5), expanded polystyrene (EPS) or extruded polystyrene (XPS), due to the need for an escape route for the gases that are released from these types of insulations.
Although probably more pronounced with self-adhesive materials, the aforementioned problems regarding lack of ventilation may occur with any of the currently used methods of roofing membrane installation. The industry has attempted to address this problem in various ways. However, none to date have been entirely satisfactory. For example, in one such installation, a slip-sheet is first mechanically fastened at various points to the substrate and the modified bituminous membrane is then installed over the slip-sheet. This “spot attachment” of the slip sheet to the deck provides a path for the escape of gases, vapor and pressure, but it is also labor intensive and adds labor and material cost to the roofing system. Another type of installation designed to provide ventilation involves the use of an asphalt impregnated and coated glass fiber base sheet having mineral surfacing on the topside and coarse mineral granules on the bottom side. Upon installation these base sheets are not solidly attached and the coarse granular surface provides an open, porous channel in the horizontal plane beneath the membrane, which allows the lateral release of pressure. These types of installations do not involve self-adhesive materials and are typically carried out by hot mopping.
With respect to self-adhesive roofing membranes, the industry has introduced self-adhesive venting base sheets, which have been in use for several years. For example, ESHAVent, produced by ESHA Holding of Netherlands, #1000 ESHAVent sold by Malarkey Roofing Company of Oregon and SOPRA ESHAVent sold by Soprema Company of Canada are self-adhering venting base sheets presently sold in the U.S. These self-adhesive membranes have a perforated aluminum foil affixed to the self-adhesive compound so that part of the adhesive is covered by the foil. A release liner is then placed over the foil to protect the remaining adhesive area. The perforation covers approximately 30% of the total area of the aluminum foil, and materials such as polyolefinic film, fabrics and glass fiber, may be used instead of aluminum foil. Saint Gobain Technical Fibers of France manufactures glass fiber reinforcement with perforations or openings for use in this application. Upon installation these membranes adhere to the substrate in only approximately 30% of the area of the sheet (i.e., through the openings in the backing), because the self-adhesive compound in the remaining approximately 70% of the area of the sheet is blocked by the aluminum foil and cannot bond to the substrate. The self-adhering venting base sheets just described were originally developed and marketed for application under hot bitumen or torch-applied systems. The non-permeable layer of aluminum foil creates an effective vapor escape channel, thereby preventing roof blistering. Moreover, the aluminum foil acts as a heat shield to protect underlying roof insulation from the heat of a torch or hot bitumen, thereby eliminating the need for a coverboard over polyisocyanurate (Polylso), expanded polystyrene (EPS) or extruded polystyrene (XPS). Such self-adhering venting base sheet membranes also have several other advantages. First, they eliminate the need for fasteners, resulting in cost savings for the applicator. Second, the absence of penetrating fasteners helps separate the roofing membrane system from the underlying insulation, thereby impeding thermal bridging which is frequent problem in temperature-controlled building such as cold-storage facilities. And finally, the spot-welded areas of the venting membrane are believed to act as shock absorbers, which compensate for the movement of the substrate (e.g. roof deck or insulation).
Though these types of self-adhering venting membranes have been used successfully for several years, they have several limitations. Because the membranes are usually 15 to 20 meters in length and are reinforced with fiberglass, the rolls into which they are formed for transport and storage become very rigid in cold conditions, especially their inner convolutions. This is exacerbated by the fact that the membranes have aluminum foil laminated to the self-adhesive compounds, which cause them to be very rigid to begin with, especially in cold weather conditions. This is a problem because unlike in torching or hot mopping installations, there is no heat involved in the installation of self-adhesive membranes, which can be used to render them more pliable in situ. Thus self-adhering membranes must be pliable enough to begin with so as to be able to upon application conform to the contours of the substrate and at intersections such as walls, flashings, roof penetrations, etc. If they are not flexible enough at the time of application, the adhesive bond between the membrane and the substrate may be affected and over time will cause the membrane to disengage from the substrate. The aluminum foil layer also adds additional raw material cost and manufacturing difficulties. For example, if the aluminum foil is not laminated properly to the self-adhesive compound during manufacture, it may disengage from the compound during packaging, transportation or field-application. Additionally, limitations in the processes of manufacture of the foil as well as lamination of the foil to the venting membrane limit the amount of perforation possible. For example, excessive perforation can lead to workability problems. One such problem is poor dimensional stability, which results in the inability to wind and then unwind the foil when laminating it to the self-adhesive compound during manufacture of the venting membrane. The area of perforation on the aluminum foil is directly proportional to the level of adhesive bond achieved between the membrane and the underlying substrate because adhesion occurs only through the perforated area. Thus process limitations which restrict the amount and the design of the open area limit the level and flexibility in level of adhesion which can be obtained.